Internal Structure Of Actuator For Differential Mode Shift

ABSTRACT

An actuator is used to longitudinally move a spline sleeve for controlling drive mode of a differential on an off-road vehicle. The actuator&#39;s motor rotates an eccentric knob through a drive train including intermediate gears and a worm gear. The eccentic knob is linked to the spline sleeve through a torsion spring carried on a pivot plate, with legs of the torsion spring pushing a slide block, transferring a moment provided by the eccentric knob into a linear slide force. The pivot plate and torsion spring are jointly mounted on the actuator housing by a hub, opposite the rotational axis of the eccentric knob from the slide block. The slide block includes a contact which completes a circuit through conductive pads on the actuator housing, so the position of the slide block can be directly sensed.

CROSS-REFERENCE TO RELATED U.S. APPLICATION(S)

None.

FIELD OF THE INVENTION

The present invention relates to drive trains in vehicles, andparticularly to mechanical locking differentials used in offroadvehicles such as UVs and ATVs.

BACKGROUND OF THE INVENTION

Utility vehicles (“UVs”) and all terrain vehicles (“ATVs”) are wellknown for travel over a wide variety of terrains, including over unpavedtrails or fields, rocks, etc. Such vehicles are widely used inagriculture and forestry operations, as well as in safety operationssuch as for rugged mountain crossings. Such vehicles are also widelyused for recreational enjoyment in natural, outdoor settings away frompavement.

In many prior art UVs and ATVs, the engine transmits power to the wheelsthrough a drive shaft, a differential, and a drive axle for each wheel.Differential drive axles of on-road vehicles must meet requirements ofvarious road conditions and complex working conditions. Examples ofdifferential drive axles for UV and ATV use are shown in U.S. Pat. Nos.4,805,486, 10,788,113 and 10,816,071, all three incorporated byreference. Many such differentials include a mechanical lockingmechanism, such as a spline sleeve which can be axially slid by ashifting fork between engaged and disengaged positions. In the engagedor locked position, one of the half shafts is rotationally secured bythe spline spleeve for rotating at the same speed as the differentialcase, and the differential then causes the other half shaft to rotate atthe same speed. In the disengaged or unlocked position, the two halfshafts can rotate at different speeds as long as their average matchesthe rotational speed of the differential case. Some such mechanicallocking differentials can have their spline sleeve shifted to a thirdposition, where neither half shaft receives torque from the differentialcase, for driving in a two wheel drive mode using the other set ofwheels.

As taught in U.S. Pat. No. 10,816,071, actuation of the shifting forkcan be powered by a small electric motor connected to the shifting forkthrough a gear train and a sliding rack. The system of U.S. Pat. No.10,816,071 is light and compact and often functions smoothly. However,positioning of the small gears in the gear train and positioning of thesliding rack needs to be quite accurate during assembly, and inaccurateassembly can cause gear slippage and/or require reassembly. If thespline sleeve, shifting fork or any gears in the gear train bind orotherwise fail to smoothly shift, the various parts can easily bedamaged, and the service life of the actuator can be lower than desired.Disassembly and reassembly of the small gear train part is particularly,difficult without fully removing the differential from the vehicle.Better options are needed.

BRIEF SUMMARY OF THE INVENTION

The present invention is an actuator for controlling drive mode of amechanical locking differential, such as between modes of two wheeldrive, four wheel drive with differential active and four wheel drivewith differential locked. The actuator has an electronic motor driving agear train within a housing. The output of the gear train includes aknob which extends outside the housing, which is eccentric relative tothe gear train output rotational axis. In one aspect, the gear trainincludes a worm gear mounted within the housing, on an opposite side ofthe gear train output rotational axis from the motor. In another aspect,the motor drives the eccentric knob between circumferential endpositions which are less than 360° of rotation apart.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the attacheddrawing sheets, in which:

FIG. 1 is a plan view, in partial cross-section, showing atwo-wheel-drive/four-wheel-drive/four-wheel-drive locked differentialstructure relative to the input bevel gear and half shafts, and showingthe actuator of the preferred embodiment of the present invention. Acircle is added to show enlarged inset views 1A showing the splinesleeve and shifting fork in the two wheel drive position, 1B showing thespline sleeve and shifting fork in the four wheel drive,differential-active position, and 1C showing the spline sleeve andshifting fork in the four wheel drive, differential-lock position.

FIG. 2 is an exploded front perspective view of the actuator of FIG. 1,looking upward from the lower right. The terms “front”, “rear”, “left”and “right”, as used herein, apply to the actuator for use on a reardifferential, merely for ease of reference when referring to thedrawings; other orientations of layouts or orientations of use, in wholeor in part, are equally possible.

FIG. 3 is an enlarged front perspective view of the output gear andshifting knob of the preferred actuator, looking downward.

FIG. 4 is an enlarged rear perspective view of the torsion spring, slideblock and slide shaft of the preferred actuator, looking downward.

FIG. 5 is a rear view of the preferred actuator of FIGS. 1 and 2 withits housing base removed.

FIG. 6A is a rear view of the electric circuit within the cover, showingthe electrical contacts in a first (in this embodiment, two wheel drive)position. FIG. 6B shows the circular trace circuit and the electricalcontacts in a second (in this embodiment, four wheel drive,differential-active) position, and FIG. 6C shows the circular tracecircuit and the electrical contacts in a second (in this embodiment,four wheel drive, differential-active) position.

FIG. 7 is a front view of the preferred actuator of FIGS. 1 and 2, afterassembly of the pivot plate, torsion spring and slide block.

FIG. 8 is a front view of the preferred actuator of FIGS. 1, 2 and 7,removing the slide block.

FIG. 9 is a side view of FIG. 8.

FIG. 10 is a front view of the preferred actuator similar to FIG. 8, butshown in the two-wheel-drive position.

FIG. 11 is a front view of the preferred actuator housing and cabling.

FIG. 12 is a rear view of the preferred actuator housing and cabling.

While the above-identified drawing figures set forth a preferredembodiment, other embodiments of the present invention are alsocontemplated, some of which are noted in the discussion. In all cases,this disclosure presents the illustrated embodiments of the presentinvention by way of representation and not limitation. Numerous otherminor modifications and embodiments can be devised by those skilled inthe art which fall within the scope and spirit of the principles of thisinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention relates to a mechanical locking differential particularlyintended for use in a drive train of a UV or ATV, with the preferredinternal structure of an example differential 10 shown in FIG. 1. Themechanical locking differential 10 has an input 12 supported on bearings14 for rotational power about a generally longitudinal axis 16 on the UVor ATV, with two outputs or axles 18, 20 mounted on bearings 22 forrotational power about a generally transverse axis 24 on the UV or ATV.The axles 18, 20 could be either for front wheels or rear wheels (notshown), and in either case the structure 10 can be reversedright-to-left. An input bevel gear 26 delivers rotational power from thevehicle engine (not shown). While the vehicle is running to power theinput bevel gear, torque is transmitted from the input bevel gear 26 toa ring gear 28 fixed to a differential case 30, with at least one pinionor planetary gear 32 positioned therein. The differential case 30 isrotationally supported within the differential bonging (not shown) byroller bearings 34. The pinion gear 32 is supported on shaft 36 torotate about the transverse axis 20 at the speed of the differentialcase 30, but can additionally rotate about its own axis 38. The piniongear 32 is in geared engagement with both side gears 40, 42, such therotational speed of the differential case 30 will always equal theaverage of the rotational speeds that the two side gear 40, 42 rotateabout transverse axis 20.

One of the side gears 40 is rotationally coupled to its axle 18 at alltimes. The other side gear 42 may or may not be rotationally coupled toaxle 20, depending upon the axial position of a spline sleeve 44, withthree axial positions 1A, 1B, 1C depicted in FIG. 1. The spline sleeve44 includes one or more inwardly facing teeth 46, which couple with oneor more outwardly facing teeth 48 on the axle 20 and at times with oneor more outwardly facing teeth 50 on the side gear 42. When the splinesleeve 44 is in the outer position 1A, the spline sleeve 44 only rideson the outwardly facing teeth 48 of the axle 20 and does not interactwith the side gear 42. Thus, in this position 1A, the side gear 42 canrotate at any speed, independent of the rotational speed of the axle 20and its wheel. With the spline sleeve 44 in the outer position 1A, anydifference between the rotational speed of the ring gear 28 and the axle18 will merely cause the pinion or planetary gear 32 to rotate about itsaxis 38, so no torque can be transmitted through the differential 10.Accordingly, with the spline sleeve 44 in the outer position 1A, thevehicle operates in a two wheel drive mode, only providing torque to theother (not shown) set of axles and wheels, such as the front wheels ifFIG. 1 depicts a rear differential 10.

The spline sleeve 44 can be shifted to a center position 1B, in whichthe spline sleeve 44 rides on the outwardly facing teeth 50 of the sidegear 42 as well as the outwardly facing teeth 48 of the axle 20, causingthe axle 20 to rotate at the identical rotational speed as the side gear42. If the vehicle is traveling in a straight line, both side gears 40,42 and both axles 18, 20 will rotate at the rotational speed of the ringgear 28 and differential case 30 about the transverse axis 24, andtorque is transmitted from the input bevel gear 26 to both axles 18, 20.When a rotational difference is caused between the outputs 18, 20 at thetime of turning or cornering of the UV or ATV, the pinion gear 32rotates around its own axis 38 to correct the rotational differencebetween the inner and outer wheels. Rotation of the pinion gear 32 aboutits own axis 38 increases the rotational speed of one of the semi-axlegears 40, 42 about the transverse axis 24 while equally decreasing therotational speed of the other of the semi-axle gears 40, 42 about thetransverse axis 24. Thus, the center position 1B of the spline sleeve 44is for a mode of four wheel drive using the differential 10.

The spline sleeve 44 can also be shifted to an inner position 1C. In theinner position 1C, the spline sleeve 44 rides on the outwardly facingteeth 50 of the side gear 42 and the outwardly facing teeth 48 of theaxle 20, while simultaneously engaging inwardly facing teeth 52 of thedifferential case 30. With the spline sleeve 44 in the inner position1C, the spline sleeve 44 thus causes the differential case 30, the sidegear 42 and the axle 20 to all rotate at the same rotational speed. Byrotationally fixing the side gear 42 to the differential case 30, thepinion gear 32 is prevented from rotating about its axis 38, and thusthe side gear 40 also rotates at the identical rotational speed as theside gear 42 and differential case 30. Torque can still be transmittedthrough the differential 10, but the differential 10 is locked. Thus,the inner position 1C of the spline sleeve 44 is for a four wheel drive,differential-locked mode.

A shifting fork 54 is used to push the spline sleeve 44 between theinner, center and outer positions 1A, 1B, 1C. Movement of the shiftingfork 54 is controlled by an actuator 56 which is the focus of thepresent invention. An exploded view of the actuator 56 is shown in FIG.2.

The actuator 56 includes a housing 58, with an electric motor 60supported within the housing 58. The electric motor 60 drives a motoroutput gear 62 as part of a gear train 64 to an output 66, which rotatesabout a gear train output axis 68. The output 66 pivotally moves a pivotlink 70, which in turn linearly moves a slide block 72 carrying theshifting fork 54. Arrows are added in FIGS. 2 and 7 to show the shiftingmotion of the slide block 72 from its center position 1B.

The slide block 72 includes a configuration adapted for mounting of theshifting fork 54. Other than in FIG. 1, the connection between the slideblock 72 and the shifting fork 54 is not shown, and the particularmounting arrangement between the slide block 72 and the shifting fork 54is not part of the present invention. In the preferred arrangement, theslide block 72 slides on a slide shaft 73 which extends through anopening in the slide block 72. The slide shaft 73 can be mounted on astationary portion of the differential 10, on the housing 58, orelsewhere from a stationary portion of the frame or rest of the vehicle,and its mounting arrangement is not shown in the figures and is not partof the present invention. Other mounting arrangements are possible forthe slide block 72 to move linearly and carry the shifting fork 54.

In the preferred arrangement, the output 66 includes an eccentric knob74, accessible on the exterior of the housing 58, attached for rotationwith the gear train output 66 about the gear train output axis 68.Movement of the knob 74 causes shifting of the differential state, sothe knob 74 can be referred to as a “shifting” knob 74. The shiftingknob 74 is offset from the gear train output axis 68, such that rotationof the gear train output 66 causes the shifting knob 74 to move fromside to side. The preferred mounting arrangement relative to thedifferential 10 mounts the actuator 56 with the gear train output axis68 extending horizontally, parallel to the input bevel gear axis 16. Theshifting knob 74 preferably extends from a rotating plate 76 of the geartrain output 66. The rotating plate 76 of the gear train output 66 ispreferably arranged continuous with an exterior profile defined by thehousing 58, such that the exterior of the housing 58 and the rotatingplate 76 jointly seal the actuator housing 58 against dirt entry intothe interior volume. For instance, after assembly the plate 76 of thegear train output 66 is coplanar with and centered within the housingcover 78.

In one embodiment, the motor only rotates in one direction. In the morepreferred arrangement, the motor 60 can be electronically controlled toselectively rotate in either direction. Using a bi-directional motor 60allows the shifting fork 54 to be moved in either direction from themiddle position 1B at any given time, merely by selecting the directionof rotation of the motor 60. In the preferred mounting arrangement, theoutput 66 rotates less than 360° between circumferential end points, andmore preferably between 90° and 180° between circumferential end points.If desired, the circumferential end points may be shown on the cover 78as shown in FIG. 11, such as by markings 79A and 79C, with the centerposition indicated by marking 79B. For instance, in the most preferredembodiment, the lowest position 79B of the shifting knob 74 (i.e., a sixo'clock position as depicted in the front view drawings) is used for thecenter position 1B of the spline sleeve 44 and shifting fork 54. Fromthis center position 79B, the motor 60 can turn to rotate the shiftingknob 74 about 62° to the right (and rotationally upward, to about a fouro'clock position 79C as depicted in the front view drawings) to bias theshifting fork 54 fully toward the inner position 1C, or about 62° to theleft (and rotationally upward, to about an eight o'clock position 79A asdepicted in the front view drawings and as shown in FIG. 10) to bias theshifting fork 54 fully toward the outer position 1A.

A primary purpose of the housing 58 is to define an interior space whichprotects the electric motor 60 and the gear train 64 from the dirt, mudand grime that they otherwise could be exposed to when mounted relativeto a drive train of an off-road vehicle such as an ATV or UV. Thehousing 58 should be light in weight while being strong and rigid. In apreferred embodiment, the housing 58 includes a base 80 and a cover 78,both of which are molded from an automotive grade polymer resin. Thecover 78 can be secured to the base 80 around the motor 60 and geartrain 64, such as using fasteners such as the machine screws 82 shown.Having the cover 78 be initially separate from the base 80 primarilyassists in manufacturing assembly of the gear train 64. Using removablefasteners 82 also allows inspection or repair of any component parts.

The housing 58 may include two or more mounting bolt holes 84 formounting the actuator 56 relative to the vehicle and relative to thedifferential 10. In the preferred embodiment, the axes for the mountingbolt hole 84 extend horizontally, which makes assembly and disassemblyon the vehicle relative to the sliding block 72 and the shifting fork 54easier.

In the preferred embodiment, the housing 58 is generally cylindrical,with the output 66 rotating about an output rotation axis 68 that iscoaxial with the cylindrical shape of the housing 58. As best shown inFIG. 2, the base 80 of the preferred housing 58 includes recesses shapedto receive the specific electric motor 60 being used as well as thevarious gears 86, 88, 90 in the gear train 64 on their shafts 92, 94. Ifdesired, the cover 78 can include complimentary recesses (not shown).Using separate recesses for supporting and aligning the electronic motor60 and each gear 86, 88, 90 in the gear train 64 helps make assembly andsupport of the gear train 64 much easier and more reliable. In the mostpreferred embodiment, motor output gear 62 and the intermediate gears86, 88, 90 and the output 66 are all primarily molded of a rigid polymerfor lightweight and ease of manufacture, but mounted to spin on metal(steel) shafts 92, 94. The various shafts 92, 94, 100 within the housing58 can be held in place by mounting plates 96 secured by screws 98.

The gear train 64 includes a significant gear reduction to reduceangular movement and increase torque of the motor output shaft to thegear train output 66. To achieve even more significant gear reduction,the preferred embodiment includes at least one worm gear 100. Forinstance, the preferred gear train 64 includes three intermediate gears86, 88, 90, with the final intermediate gear 90 driving the worm gear100. The gear train 64 preferably provides a gear reduction of at leastten times, and the worm gear 100 provides a gear reduction of at leastten times, i.e., to complete a 180° throw of the output 66, the motorshaft would rotate at least 50 revolutions. In the most preferredembodiment, the output gear 62 of the motor 60 has about 10 teeth, andprovide about a 3/1 a gear reduction to the first intermediate gear 86which has about 30 outer gear teeth and 12 inner gear teeth, providingabout a 3/1 gear reduction to the second intermediate gear 88 which hasabout 36 outer gear teeth and 12 inner gear teeth, providing about a 4/1gear reduction to the third intermediate gear 90 which has about 48outer gear teeth, i.e, the gear train 64 in the most preferredembodiment provides about a 36× gear reduction. The worm gear 100 in themost preferred embodiment drives a gear 102 with about 24 teeth, i.e.,the worm gear 100 provides about a 24× gear reduction. In the mostpreferred embodiment, a complete throw of the output 66 (which moves thespline sleeve 44 from the inner position 1C to the outer position 1A),is about 125°. Thus, in the most preferred embodiment, to completemovement of the spline sleeve 44 from the inner position 1C to the outerposition 1A, the motor shaft rotates about 300 revolutions.

To best utilize the space within the cylindrical housing 58, the wormgear 100 is preferably mounted on an opposite side of the output axis 68as the motor 60. For instance, in the most preferred arrangement, boththe motor output shaft axis and the worm gear axis extend vertically.The worm gear axis is offset relative to the gear train output axis 68on an opposite side from the motor output shaft axis.

The motor 60 has electric leads which extending outside the housing 58,at a minimum to supply electric power and a return path (which could beby grounding of the housing 58, if at least a portion of the housing 58conducts electricity) to the motor 60. Preferably the power driving themotor 60 is in accordance with the electrical system of the vehicle,such as a 12 V DC system. The preferred leads include a cable 104 with aplurality of signal wires connectable with a standard automotive plug106, with a separate grounding wire path 108. While a microcontrollercould be included within the actuator 56, the preferred embodiment doesnot include any microcontroller or other logic circuit, and instead theelectrical system within the actuator 56 is entirely carried along wiresand/or signal traces. To make manufacturing easier and reduce costs, theelectrical circuits in the preferred actuator 56 are entirely supportedby the cover 78, with the interior circuitry best understood withreference to FIG. 6A-6C and the exterior circuitry be understood by FIG.11 in combination with FIG. 4. Both the signal cable 104 and thegrounding wire 108 connect into and through the housing cover 78 ratherthan into or through the housing base 80.

The preferred embodiment includes three separate circuits arrangementswithin the cover 78. One circuit arrangement provides power for themotor 60 at a higher voltage and/or amperage than necessary for theother two circuit arrangements. As shown in FIG. 6A, the cover 78supports two power contacts 110 for the motor 60, which make contactwith contacts 112 on the motor 60 when the cover 78 is assembled overthe motor 60 and base 80. One of these contacts 110 is connected intothe ground wire 108. The other contact 110 is controlled outside theactuator 56, preferably providing power to the motor 60 at appropriatetimes at positive or negative 12V relative to the ground wire 108 forturning the motor 60 in one direction or the other.

If desired, to control how long the motor 60 runs to drive the shiftingknob 74 between positions 79A, 79B, 79C, the motor 60 could becontrolled by timing (on duration before turning off), or could be astepper motor controlled by number of forward/reverse revolutions of themotor output shaft. In the preferred embodiment, however, the positionof the shifting knob 74 is more directly assessed through a circuitwhich involves a plurality of electronic contacts 114 (in the preferredembodiment, three conductor legs 114A, 114B, 114C) mounted on the geartrain output 66. As the gear train output 66 rotates, each contact 114slides along a stationary circular arc trace circuit 116 printed on theinside surface of the housing cover 78. The circular trace circuit 116is provided in four parts 116A, 116B, 116C, 116D, each of which is anexposed electrical conductor. The electric contacts 114 mounted on thegear train output 66 are all merely conductive with each other,connecting two (or three, when in between positions) of the four parts116A, 116B, 116C, 116D of the trace circuit 116. If desired, thissliding contact circuit could be directly part of the power circuit forthe motor 60, such as supplying the +−12V signal at the amperagerequired by the motor 60. In the preferred embodiment, the slidingcontact circuit is operated at a lower amperage and voltage, therebyreducing power loss and not being tied to either the voltage or amperagerequired to drive the motor 60. The preferred embodiment is less costlythan many other embodiments because it requires no memory of the last orcurrent position of the output 66.

As drawn in this embodiment, the innermost trace 116A provides one sideof the circuit, with the other three traces 116B, 116C, 116D provide theother side of the circuit. In the most preferred form, when it isdesired to move to four-wheel-drive-differential-in-use mode (i.e., tothe position shown in FIG. 6B, from either the position shown in FIG. 6Aor the position shown in FIG. 6C), the clockwise middle trace 116B issupplied with high positive voltage and the counterclockwise middletrace 116C is supplied with high negative voltage relative to theinnermost trace 116A. The motor 60 stops when the middle contact 114Bhits the gap between the two middle traces 116B, 116C, when neither ofthe high traces are conductive with the output trace 116A. When it isdesired to shift to two-wheel-drive mode (i.e., to the position shown inFIG. 6A, from either the position shown in FIG. 6B or the position shownin FIG. 6C), the counterclockwise middle trace 116C and the outermosttrace 116D are supplied with high negative voltage relative to theinnermost trace 116A. At the position shown in FIG. 6C, thecounterclockwise middle trace 116C is connected to the output(innermost) trace 116A and starts the motor 60. At the position shown inFIG. 6B, the outer trace 116D is connected to the output (innermost)trace 116A and either continues or starts the motor 60. The motor 60stops when the outer contact 114C moves past the end of the outermosttrace 116D, when neither of the high traces are conductive with theoutput trace. When it is desired to move tofour-wheel-drive-differential-lock mode (i.e., to the position shown inFIG. 6C, from either the position shown in FIG. 6A or the position shownin FIG. 6B), the middle clockwise trace 116B and the outermost trace116D are supplied with high positive voltage relative to the innermosttrace 116A. The motor 60 stops when the outer contact 114C moves pastthe other end of the outermost trace 116D, when neither of the hightraces are connected to the output trace. Thus, the connection betweenthe contacts 114 and their trace circuit 116 is used interrupt power toone of the electric leads of the motor 60 when the gear train output 66has completed a desired throw of less than 360°.

If desired, the circular trace circuit 116 can also be used as a sensingcircuit, with connectivity between the four parts 116A, 116B, 116C, 116Dtested or sensed to determine the circumferential position of the output66. However, such an arrangement does not necessarily tell the positionof the sliding block 72 and spline sleeve 44, which could differ fromthe circumferential position of the output 66 due to the construction ofthe pivot link 70, described further below. The preferred embodimentincludes a third separate electric circuit, which includes three wires118 each connected to one of three conductive pads 120A, 120B, 120C.Each conductive pad 120A, 120B, 120C extends through the wall of thecover 78, exposed on the outside of the housing 58. The position of theconductive pads 120A, 120B, 120C correspond with the position of thesliding block 72 when the spline sleeve 44 is in each of the threepositions 1A, 1B, 1C. In other words, the conductive pads 120A, 120B,120C provide stationary contacts including a two-wheel-drive contactpoint 120A, a four-wheel-drive contact point 120B and a four-wheel-drivelock contact point 120C, all of which are aligned in a line parallel tothe linear motion of the slide block 72. As best shown in FIG. 4, thesliding block 72 includes a spring loaded contact 122, which slidesalong the outside face of the cover 78. Further, the spring loadedcontact 112 is preferably grounded, such as through the shifting fork54, spline sleeve 44 and differential 10. Thus, when the sliding block72 is in the position 1A, the circuit through the conductive pad 120A iscompleted. When the sliding block 72 is in the position 1B, the circuitthrough the conductive pad 120B is completed. When the sliding block 72is in the position 1C, the circuit through the conductive pad 120C iscompleted.

All of these various signals/wires are transmitted through the signalcable 104, for use and/or control in a microcontroller or processor (notshown) elsewhere in the vehicle. For instance, the vehicle may have acontrol unit (not shown) which can detect if the rotational differencebetween the left and right wheels increases beyond the threshold seen inmere cornering. If one of the wheels is caught by mud or suspendedairbourne while in four-wheel-drive-using-differential mode, theincreased rotational difference is detected by the control unit, whichsends the electrical signal to drive the motor 60 shifting the splinesleeve 44 to the differential lock position.

While many aspects of the present invention can use other types oflinkages, the preferred connection between the shifting knob 74 and thesliding block 72 is provided by the pivot link 70. The pivot linkage 70transfers a moment provided by the shifting knob 74 into a linear forceon the slide block 72. The pivot link 70 pivots about a pivot axis 124which is parallel to the output axis of rotation 68. While the pivotlink 70 could alternatively be mounted on a stationary portion of thedifferential 10 or from a stationary portion of the frame or rest of thevehicle, the preferred arrangement mounts the pivot link 70 on thehousing 58. More particularly, the preferred pivot link 70 includes apivot plate 126 and a torsion spring 128, both jointly mounted on a hub130 for pivoting about the pivot axis 124. A screw 132 can be used toremovably mount the hub 130 to the cover 78 of the housing 58. The hub130 makes assembly easy and helps maintain alignment of both the torsionspring 128 and the pivot plate 126.

The pivot plate 126 includes a slot 134 which slidingly receives theshifting knob 74. Movement of the shifting knob 74 thus causes the pivotplate 126 to pivot about the pivot axis 124. The pivot plate 126 holdsthe torsion spring 128. In the preferred embodiment, the torsion spring128 includes two legs 136, ends of which are positioned around sidesurfaces 138 of the slide block 72. Middle portions of the two legs 136are positioned around a neck 140 at the distal end of the pivot plate126. The legs 136 extend radially relative to the pivot axis 124. Whenthe pivot plate 126 is pivoted due to side to side motion of theshifting knob 74, the neck 140 pushes on one of the legs 136 of thetorsion spring 128, biasing the torsion spring 128 toward pivoting withthe pivot plate 126. The other leg 136 of the torsion spring 128 in turnpushes on the slide block 72, tending to resist pivoting.

Binding can occurs at times during sliding of the spline sleeve 44 intoengagement with the side gear 42 or into engagement with thedifferential case 30, when the teeth 46, 50, 52 do not line up,temporarily preventing longitudinal movement of the spline sleeve 44.Shifting the position of the spline sleeve 44 can accordingly bedifficult. Using the torsion spring 128 to transfer the motion producedby the motor 60 on the shifting knob 74 to the sliding block 72 givesthe actuator 56 a way to absorb such binding or shifting difficulty,without stressing the motor 60 or the gear train 64. The spring 128 canstore a force provided by the moment of the shifting knob 74 as it movesrotationally and later use that stored force to move the slide block 72and the spline sleeve 44 in the longitudinal direction. Thus, using ofthe spring 128 within the pivot link 70 enables the use of a lessexpensive/powerful and smaller motor 60 and less expensive and smallergears 62, 86, 88, 90, 100, 102 in the gear train 64.

As noted above, the potential for binding and the operation of thespring 128 means that the position of the slide block 72 may not alwaysmatch the position of the shifting knob 74. Because the preferredactuator 56 can electrically sense this positional discrepancy, thesensing can also be used such as in an engine control unit (ECU), whichcan temporarily reduce or otherwise control the torque or rotationalspeed being output by the bevel gear 26 until the spline sleeve 44 fullyshifts.

The pivot plate 126 includes an overbar 142 which captures and holds thetwo radially extending legs 136 around the neck 140. Due to the overbar142, the plate 126 contacts each radially extending leg 136 both on aside toward the motor 60 and on a side away from the motor 60, tomaintain alignment of the torsion spring 128. Assembly of the torsionspring 128 relative to the pivot plate 126 by inserting the legs 136under the overbar 142 is easily done before mounting both the torsionspring 128 and pivot plate 126 to the housing cover 78 using the hub130. After the torsion spring 128 has been assembled to the pivot plate126, the pivot plate 126 makes damage to the alignment of the legs 136of the torsion spring 128 much less likely, and maintains the alignmentof the torsion spring 128 both to the pivot axis 124 and to the slidesurfaces 138 of the sliding block 72.

The preferred mounting arrangement places the pivot axis 124 on theopposite side of the output axis 68 from the sliding block 72. That is,the pivot link 70 has a middle portion which receives the shifting knob74 and an end portion engages the push surfaces 138 of the sliding block72. When mounted in this location, the housing 58 tends to protect boththe entirety of the pivot link 70 and the sliding block 72 from damage.Additionally, when mounted in this location, the distance of side toside motion of the sliding block 72 is greater than the distance of sideto side motion of the shifting knob 74. The slide block 72 moves in aslide block movement direction, shown by arrows in FIGS. 1 and 7, whichis perpendicular to a line intersecting both the output link axis ofrotation 68 and the pivot axis 124.

The present invention thus provides a simple, low cost, lightweightactuator 56 for moving the spline sleeve 44. It readily providesinformation about the position of its components. It is easy toassemble, and very reliable in use, even in the rugged environment ofATV or UV usage.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. An actuator for mechanically controlling drive mode of a differentialin a drive train on an off-road vehicle, the actuator comprising: ahousing adapted to be mounted relative to the drive train of theoff-road vehicle adjacent the differential, the housing defining aninterior volume and an exterior; an electronic motor mounted within theinterior volume of the housing, the electronic motor rotatably driving amotor output shaft within the interior volume, the motor having electricleads extending outside the housing; a gear train mounted within theinterior volume of the housing and driven by the motor output shaft toreduce angular movement and increase torque of the motor output shaft toa gear train output, the gear train output being rotatable about a geartrain output axis; and an eccentric actuator output, accessible on theexterior of the housing, attached for rotation with the gear trainoutput about the gear train output axis, the eccentric actuator outputbeing offset from the gear train output axis.
 2. The actuator of claim1, wherein the actuator further comprises: a plurality of electroniccontacts mounted on the gear train output, which electronic contactsinterrupt at least one of the electric leads when the gear train outputhas completed a throw of less than 360°.
 3. The actuator of claim 2,wherein the electric leads comprise at least two exposed stationaryconductors each extending in an arc about the gear train output axis onan inside surface of the housing, and rotating conductors making slidingcontact with the stationary conductors as the gear train output rotates.4. The actuator of claim 3, wherein the housing is cylindrical, centeredon the gear train output axis.
 5. The actuator of claim 1, wherein thegear train comprises at least one worm gear.
 6. The actuator of claim 5,wherein the housing comprises mounting bolt holes defining mounting bolthole axes which extend horizontally, wherein the gear train output axisextends horizontally parallel to the mounting bolt holes, and whereinthe motor output shaft rotates about a motor output shaft axis whichextends vertically and is offset relative to the gear train output axis.7. The actuator of claim 6, wherein the worm gear rotates about a wormgear axis, and wherein the worm gear axis extends vertically and isoffset relative to the gear train output axis on an opposite side fromthe motor output shaft axis.
 8. The actuator of claim 5, wherein theworm gear provides a worm gear gear reduction of at least ten times. 9.The actuator of claim 8, wherein the gear train provides a gear traingear reduction of at least ten times, in addition to the worm gear gearreduction.
 10. The actuator of claim 1, wherein the eccentric actuatoroutput is a shifting knob extending from a rotating plate of the geartrain output, and wherein the plate is arranged continuous with anexterior profile defined by the housing, such that the exterior of thehousing and the rotating plate jointly seal the actuator housing againstdirt entry into the interior volume.
 11. The actuator of claim 1,wherein the housing comprises a base and a cover, and wherein the basecomprises separate recesses for supporting and aligning the electronicmotor and each gear in the gear train.